The invention relates to a device for emulating a microcontroller, comprising a parent microcontroller in a bond-out version which comprises:
a first series of standard pins, corresponding to those of a non-bond-out version, for executing input/output operations, PA1 a second series of memory connection pins for exchanging data, addresses and control signals with an external program memory, PA1 a third series of connection pins for exchanging control signals with an external hardware register, PA1 a processor element, PA1 and communication means between said processor element, said plurality of series of pins, and further parts of the parent microcontroller.
A microcontroller is to be understood to mean an integrated circuit which comprises a processor element, means for sequentially applying control signals of a program to the processor element, exchange means for exchanging user signals between the environment and the microcontroller, and a bus for communicating user signals between the exchange means and the processor element. Other facilities may also be provided. In a standard (non-bond-out) version, the program is stored in a part of the microcontroller, for example in a read-only memory (ROM) or in an EPROM whose contents can be written once, after which it cannot be electrically modified. Furthermore, a variety of further facilities may be added in order to enable or improve the operation in a user environment. For each user application of the microcontroller a specific control program is required. This program is designed in phases. After a preparatory phase, a program is loaded and it is stepwise checked whether the successive instructions are correct. In order to enable correction of any errors, such an emulation phase utilizes an external memory, for example a random access memory (RAM) or an EEPROM. To this end, a "bond-out" version is developed from the standard version of the microcontroller; therein additional external connection pins (address, data and control pins) are provided, while the internal program memory is completely or partly absent. A microcontroller of this kind is described in "Single-chip 8-bit microcontrollers USER MANUAL", Philips Electronic Components and Materials Division, International Business Relations, P.O. Box 218, Eindhoven, the Netherlands, 1986, pages 323 ff. The standard pins are stated on page 329. The memory connection pins for the external program memory are stated on page 330. The control pins for the emulation procedure are stated on page 331: HALT, INTA, DXALE, IFF, STFF. Finally there is provided a series of connection pins for exchanging control signals with an external hardware register: DXRD, DXWR, EXDI. Each respective user application in principle requires only one specimen of a bond-out version; moreover, this single specimen can in principle be used for a plurality of user functions. The number of specimens of the standard version is in principle unlimited for each user function. Therefore, the development costs of the bond-out version generally bear on a comparatively small number of specimens.
Usually derivative versions are formed from such a microcontroller. These derivatives may differ from one another in a variety of ways, for example in that there is provided an additional external general-purpose connection (port), a connection facility for a display element (LCD), for a keyboard, and the presence of more or less storage capacity for program information or data. Many other possibilities also exist. Notably an additional amount of derivative logic will then be present.
The emulation of each derivative version in principle also requires a respective bond-out version. This necessitates an additional development effort. It is an object of the invention to provide means which allow for this emulation to be performed by means of a "bond-out" version of a parent microcontroller and a normal specimen of the derivative version with an extremely small number of modifications, notably the number of additional pins, for both versions.
The bond-out version is normally used also for manufacturing a prototype. In that case the external program memory is connected to the microcontroller by way of a so-called "piggy-back" connection. The same integrated circuit is then used, albeit the connections of this chip to the pins of the envelope differ from those used for the emulation. The difference between this approach and the emulation consists in that the physical dimensions of microcontroller plus external program memory deviate only slightly from those of the standard version (for example, the microcontroller can be used in a physically realistic environment) and in that the events in the time domain take place at the intended speed, so that a variety of situations which marginally function during the emulation phase and which would fail in normal operating conditions will now also fail at an early stage.